ESD (ElectroStatic Discharge) is a significant threat to quality in the electronics industry. Major companies state that 25% of all unidentified failures of electronic equipment result from damage caused by ESD. In total, ESD-related failures are estimated to cost the industry billions of dollars annually.
Investing in a high-quality ESD control plan has been shown to deliver typical ROI from 5:1 up to 20:1 according to articles in the compliance press. One hightech company recently reported equivalent savings of €95 for every €1 spent on ESD protection.
An ESD protection plan meeting international standards can be implemented using relatively inexpensive equipment. To remain effective, it needs to be continuously monitored and improved. ElectroStatic charge generation increases significantly as relative humidity decreases; so typically if mysterious quality and reliability problems are observed in products manufactured during your lowest humidity season, it’s likely to be ESD related.
Need for a Plan
Most firms use the EN61340-5-1 standard to construct their ESD control plan. The standard addresses grounding and bonding systems, personnel grounding, protective packaging, and marking. In addition to setting out a control program plan, EN61340-5-1 also describes requirements for ESD training and compliance verification.
Specified grounding measures include wrist straps for seated operators, as well as ESD flooring and ESD footwear such as foot grounders for standing or mobile workers. Insulators in the ESD Protected Area (EPA), however, cannot be discharged by grounding. EN 61340-5-1 clause 5.3.3 states that “All non-essential insulators (plastics and paper) such as coffee cups, food wrappers and personal items shall be removed from the workstation or any operation where unprotected ESDS items are handled.”
Process-essential insulators present in the EPA can present significant ESD threats such as Field Induced Discharges. These can occur even at a properly grounded ESD work surface. According to IEC61340-5-1, the electrostatic field at the position where the ESDS device is handled must not exceed 10,000V/m. All insulators with electrostatic potential greater than 2kV must be kept a minimum of 30cm from the device. If the measured electrostatic field or surface potential exceeds the stated limits, ionisation or other techniques must be used. By generating positive and negative ions, which are attracted or repelled by the charge accumulated on the insulator, an air ioniser can neutralise an insulator in a matter of seconds.
The third fundamental principle of the ESD control system covers packaging. Shielding bags or containers having a conductive outer surface are commonly used. To be effective, bags and containers should be closed, and opened only by a grounded operator at an ESD workstation.
Conclusion
All ESD control costs should provide the user with improved quality and reliability. To maximize ROI, highest loss operations, areas and products should be identified and addressed first. By keeping ESD Control an on-going quality process, program costs and resulting ROI can be monitored so that the company can maximize total program value. Businesses that get ESD right will see a direct and measureable contribution to their bottom line, as well as an improvement in customer satisfaction.
For more information download the Charleswater ESD Awareness Booklet
Article taken from eTech issue 5
